Well, what people wear could have an indirect effect on the flow of some rivers, in that cotton plants require a vast quantity of water - a quick google reveals that the quantity of cotton to make one shirt requires 400 gallons of water to grow. So the less people wear, the better.

However, to address your questions, there are clearly various issues here: individual freedom to wear whatever we wish, vs collective identity in terms of dressing in a way which is acceptable to our culture. Linked to that is the moralistic aspect - not necessarily religious, nonbelievers have a sense of decency too. Religion of course brings in all sorts of ideological control issues. I don't have strong opinions about what other cultures choose to wear, except that I dislike seeing people with their faces covered.

Personally, on those rare hot and sunny days we get, I wish that most people wouldn't strip off so much, because regardless of gender not many people look good in the flesh - but that's an aesthetic viewpoint!

There is an irony in our culture that despite having complete freedom to wear whatever we wish, subject to fairly minimal decency standards, we generally conform quite closely to what our peer group expects - and this applies particularly to the young, despite their enthusiasm for personal freedom in such matters.